Help seriously needed

Hi all

After having performed crucial hotfixes over the last couple of
months, a lot of the XP-pc's at our office-domain have begun denying
remote login. By chance we discovered that the setting "allow logon
through terminal services" (in local security policies/user rights) is
suddently blank on the XP-terminals in the domain. Apart from
performing crucial updates we have NOT changed any settings at the
domain-server or anywhere else, but is seems like something in the
updates add or modifies a global policy making the mentioned setting
in local policies (allow logon through terminal services) go and
remain blank.
We're in deep trouble here any help is more than welcome.

Best regards

/T